to make more harsh, uncompromising, or severeplans to further stiffen the already onerous requirements for admission to the elite military unit
plans to further stiffen the already onerous requirements for admission to the elite military unit
harden, harshen, strengthen, toughen
ameliorate, ease
lessen, moderate, soften
in the 15th century
英语同义词词典收录了63618条英语词条，基本涵盖了全部常用同义词或反义词的辨析及翻译，是英语学习的有利工具。